Many products are encapsulated for convenience in distribution and use. Among these are medicinal compounds, such as drugs or vitamins, which are commonly encased in gelatin capsules. Capsules are also used when small, accurately determined quantities of material are to be used in compounding other products, such as for example, small capsules of food coloring for combining with artificial food products to produce a desired color. Such capsules may be filled with either a powdered material or a liquid, or even possibly a combination of such materials.
While a number of prior art arrangements are known for the manufacture and production of gelatin capsules either for powdered material or a liquid, such prior art arrangements generally are not readily adaptable for filling of capsules with both powdered material and a liquid. Rather, such prior art arrangements are generally only directed to the utilization of a fill powder or a fill liquid.
For instance, U.S. Pat. No. 3,092,942 entitled "Apparatus for Encapsulating" to Chasman is directed to a machine and method for making fluid filled capsules from continuous sheets of plastic film. However, the machine disclosed in this patent is not readily adapted to filling the capsules with a dry fill powder. On the other hand, U.S. Pat. No. 2,775,084 is directed to an apparatus for filling capsules with a powder material. Again, however, such apparatus is not readily adaptable for filling the capsules with a fluid or liquid.
Generally, in many of the prior art capsule forming apparatus and methods, a pair of plastic webs, for example webs of gelatin material, are fed about a pair of sealing rolls having a series of depressions or recesses formed in the surface thereof. The recesses in each sealing roll may be connected to a suitable source of vacuum for applying a suction to the web when it is laid onto the surface to thereby form a series of cavities or pockets in the surface of the web. The depressions or recesses in the sealing rolls are arranged with respect to one another and the sealing rolls driven in unison and synchronized with one another so that as the sealing rolls are rotated in opposite directions, the depressions on one sealing roll register with the depressions on the other sealing roll in the nip of the two rolls. Thus, as the webs are directed toward the nip of the sealing rolls, the pockets or cavities formed in the web traveling on one roll are brought into juxtaposition with the pockets or cavities formed in the other web. That as, as the webs progress through the nip, the portions of the respective webs surrounding each depression are pinched together to essentially create a seal about the pair of juxtaposed pockets or cavities and thereby form a completed capsule. Generally, either a liquid or dry powder material is deposited into one or both of the cavities of the respective webs just prior to the two webs being brought into juxtaposition and sealingly closed.
While a number of of such apparatus of this general nature are known, a number of problems have existed with such prior art apparatus, both with respect to the dry fill type apparatus and the liquid fill type apparatus. For example, one significant problem associated with conventional powdered fill capsule forming apparatus has been the sealing of the capsule halves together with the pharmaceutical product therein. In particular, prior art powder filled capsules have had a tendency, after drying of the gelatin casing, to break open along the sealed seam and thereby spill the contents thereof. Such problems in sealing of the capsule halves has been due, at least in part, to the fact that dust or other powdered materials have spilled or been deposited on the web of the fresh gelatin material about the cavity or pocket formed therein during the fill operation. Such spillage in turn presents a tight, effective and sound seal from being formed when the web of the material passes between the nip of the sealing rolls.
A further problem associated with conventional powdered fill capsule forming apparatus has been the precise control of the amount of material deposited into the capsule, both from the standpoint of initial measurement of the amounts as well as from the standpoint of spillage or loss of such material in depositing the fill material into the capsules halves. For instance, in the apparatus shown in British Patent Specification No. 881,022, entitled "Improvements Relating to Methods and Machines for Forming and Filling Capsules in Gelating or the Like", there is disclosed an apparatus of the general type described above in which capsule halves are formed from gelatin webs and then brought into juxtaposition and sealed after the placement of a dry fill powder in each cavity half. In this apparatus, there is provided a medicament supply hopper containing a supply of fill powder above each of the sealing rolls. A rotary feed roll is disposed between each supply hopper and its respective sealing roll for receiving a supply of powder from the hopper and depositing same in the capsule halves. The feed roll has at its periphery axial and circumferential rows of chambers which are spaced so as to coincide with the spacing of the cavities on its respective sealing roll. The chambers each include a spring loaded plunger or ejector therewithin which is normally in a retracted position. As the feed roll rotates, the chambers which are in alignment with the hopper are supplied with powder or granules of material to be encapsulated. The size of the chamber is designed so that it will receive a desired quantity of material. The filled chambers are then rotated within a stationary annular housing which serves to maintain the charge of powder material within the chamber. An opening is provided at the bottom of the annular housing through which the powder material in the chamber is deposited into a cavity on the sealing roll when the chamber moves into alignment therewith. A cam member is provided for forcing the plunger outwardly against the spring to ensure that the fill material is ejected from the chamber and into the cavity formed in the web on the sealing roll. As can be appreciated, with such an arrangement, it is most difficult to change or adjust the amount of fill material which is received within each chamber, and further there is a possibility that the chamber will not be completely filled, or that powder or fill material will be lost during the transfer from the feed roll into the cavity since the fill material is only loosely received in the chambers.
Additionally, as is known in the art, some types of fill materials, especially certain types of liquid, such as vitamins, when exposed to air over a period of time, deteriorate and may become rancid. As can be appreciated, since the cavity halves in each web are open and exposed to the surrounding atmosphere during the filling operation, it has not been possible heretofore to produce capsules having such fill materials with conventional capsule forming apparatus of the type disclosed unless the entire capsule forming apparatus is operated in an inert atmosphere.
Still further, with some prior art capsule forming apparatus, the gelatin web is formed by depositing molten gelatin onto a rotating casting drum which is at a somewhat cooler temperature to solidify the gelatin and form a web which is then continuously pulled off of the drum. With such prior art arrangements, the gelatin supply box rests directly on the gel forming surface of the casting drum and molten gelatin flows onto the drum as it is rotated, the thickness of the layer of gelatin being controlled by a "doctor" blade arranged at the forward end of the gelatin supply box. Generally, the doctor blade is carried by the gelatin supply box, and its position above the surface of the casting drum, which defines the thickness of the formed gelatin web, is adjustable. Since the gelatin supply box rides on the surface of the casting drum, should a film or very thin layer of gelatin remain on the casting drum during operation, the thickness of the formed gelatin web may not be precisely accurate. Furthermore, as the adjustment mechanism for adjusting the position of the doctor blade is on the gelatin supply box itself, there is a possibility of damage, breakage, etc., when the gelatin supply box is cleaned between operations.
Accordingly, in view of the above and other disadvantages, a need exists for improved methods and apparatus for forming capsules, as well as for forming webs for use in capsule manufacture.